JP4960574B2 - Refractory used for continuous casting nozzles to prevent alumina adhesion - Google Patents
Refractory used for continuous casting nozzles to prevent alumina adhesion Download PDFInfo
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- JP4960574B2 JP4960574B2 JP2003117580A JP2003117580A JP4960574B2 JP 4960574 B2 JP4960574 B2 JP 4960574B2 JP 2003117580 A JP2003117580 A JP 2003117580A JP 2003117580 A JP2003117580 A JP 2003117580A JP 4960574 B2 JP4960574 B2 JP 4960574B2
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- clinker
- graphite
- cao
- alumina
- refractory
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 title claims description 29
- 238000009749 continuous casting Methods 0.000 title claims description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 38
- 229910002804 graphite Inorganic materials 0.000 claims description 35
- 239000010439 graphite Substances 0.000 claims description 35
- 239000002245 particle Substances 0.000 claims description 23
- 239000011819 refractory material Substances 0.000 claims description 11
- 230000003405 preventing effect Effects 0.000 claims description 8
- 239000011159 matrix material Substances 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- 238000005266 casting Methods 0.000 description 9
- 238000000034 method Methods 0.000 description 8
- 229910000831 Steel Inorganic materials 0.000 description 7
- 239000010959 steel Substances 0.000 description 7
- 230000003647 oxidation Effects 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 6
- 239000010459 dolomite Substances 0.000 description 5
- 229910000514 dolomite Inorganic materials 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 230000002265 prevention Effects 0.000 description 4
- 239000003963 antioxidant agent Substances 0.000 description 3
- 230000003078 antioxidant effect Effects 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 230000008034 disappearance Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical group [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- 229910000655 Killed steel Inorganic materials 0.000 description 2
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000029087 digestion Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 238000004898 kneading Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002689 soil Substances 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- 229910000532 Deoxidized steel Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000003064 anti-oxidating effect Effects 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 239000012237 artificial material Substances 0.000 description 1
- 235000010216 calcium carbonate Nutrition 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 1
- 235000019341 magnesium sulphate Nutrition 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 239000000289 melt material Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 239000005011 phenolic resin Substances 0.000 description 1
- 239000011295 pitch Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 229920002050 silicone resin Polymers 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
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- Continuous Casting (AREA)
- Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
- Compositions Of Oxide Ceramics (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は溶鋼の鋳造に際して使用するストッパー、ロングストッパーを含むスライディングノズル、上ノズル、下ノズル、中間ノズル、浸漬ノズル等の連続鋳造用ノズルに用いられるアルミナ付着を防止する耐火物に関する。
【０００２】
【従来の技術】
近年、とくに薄板等の高級鋼として鋳造されるアルミニウムで脱酸された鋼、いわゆるアルミキルド鋼の鋼材品質の厳格化に伴い、連続鋳造においてタンディッシュからモールドに注入するために使用されるノズルへのアルミナ付着の防止に多くの努力が払われている。
【０００３】
ノズルに付着したアルミナは合体して、それが溶鋼流に大型の介在物として取り込まれて鋳片の欠陥となり品質を低下させることになる。
【０００４】
その対策の一例として、ノズルの内面からアルゴンガスを溶鋼中に吹き込んで物理的にアルミナの付着を防止する手法がある。しかしながら、この手法はアルゴンガスの吹き込み量が多すぎると気泡が鋳片内に取り込まれて鋳片中のピンホールとなる。従って、鋳片中の欠陥の発生を防止するために、ガスの吹き込み量を制限しなければならず、この手法はアルミナの付着を防止ための十分な対策とはなり得ない。
【０００５】
また、その他の対策の例として、連続鋳造において使用されるノズル等を構成する耐火材にＣａＯを含有させてアルミナ付着防止機能を持たせ、耐火材中のＣａＯとノズルに付着したアルミナとを反応させて低融物を生成してアルミナの付着を低減させる手法も知られている。例えば、特許文献1には、この手法を発展させた形態として、アルミナ付着防止機能と耐熱衝撃性を高めたドロマイトクリンカーと黒鉛とを炭化されたマトリックス組織で結合した耐火材を適用したノズルが開示されている。
【０００６】
しかしながら、このノズルはそれ自体は、優れたアルミナ付着防止機能を有する反面、予熱条件によっては表面が酸化して炭素が消失し、そこに発生した窪みにメタルが沈積し、その上にアルミナが付着してしまい、折角のドロマイトクリンカーによるアルミナ付着防止能が失われてしまう。
【０００７】
この予熱時の酸化による表面炭素の消失は、酸化防止材として、溶融してガラス被膜を形成するガラスフリットを含有する粉末を、ノズル表面に塗布することが効果的であるといえる。
【０００８】
ところが、ノズルにＣａＯを多量に含有する耐火材を使用する場合、耐火材中のＣａＯが、溶融した酸化防止材中に拡散してガラス被膜の粘性を低下させ、このため、被膜が破れたり、ノズルに吸収されたりして酸化防止機能が十分発揮されない場合がある。この様な現象は、予熱温度が高い場合や予熱時間が長い場合にとくに生じ易い。とくに、連続鋳造ノズルに適用されているＣａＯ−ＭｇＯ系クリンカー、すなわち、ドロマー黒鉛系耐火物は、前記特許文献１に記載のように、黒鉛の含有量が３８重量％以上と多い割には、使用しているドロマの粒度は比較的大きいものが使用されている。そのため、黒鉛間に存在するドロマ粒子の数が少なくなり、黒鉛同志が重なり合って大きな固まりとして存在する割合が多くなる。この黒鉛同志が重なり合った大きな固まりは、予熱時に酸化されると黒鉛の消失によって大きな窪みが多数発生し、そこにメタルが侵入して固着し易くなる。メタルが固着すると、付着したアルミナへの耐火材からのＣａＯの拡散が妨げられるのでアルミナが堆積することになる。
【０００９】
【特許文献１】
特表平１１−５０６３９３号公報
【００１０】
【発明が解決しようとする課題】
本発明の課題は、黒鉛およびＣａＯ−ＭｇＯ系クリンカーを主成分とする連続鋳造用耐火物において、予熱時に黒鉛が酸化消失した場合のアルミナ付着防止効果の低減を防止することにある。
【００１１】
【課題を解決するための手段】
本発明は、ＣａＯ含有系耐火物を使用したノズルの場合、このように、酸化防止材によって予熱時の酸化を完全に防止することは困難であり、耐火物自身にも黒鉛の消失を前提とした対策を取っておくことが、長期間の安定鋳造に寄与するという認識の下で完成した。
【００１２】
すなわち、本発明は、ＣａＯ−ＭｇＯ系クリンカーおよび黒鉛を主成分とする耐火物において、クリンカーの平均粒度を黒鉛の含有量に合わせて制御するもので、耐火物中の黒鉛の含有量をａ（質量％）、ＣａＯ−ＭｇＯ系クリンカーの平均粒度をｂ（ｍｍ）とした場合に、前記ａとｂとの関係が下記（１）式を満足することを特徴とする。
【００１３】
ｂ≦−０．０２×ａ＋０．８ （１）
本発明は、黒鉛およびＣａＯ−ＭｇＯ系クリンカーを主成分とする耐火物において、予熱によって黒鉛が消失した際に生成する窪みを小さくするには、黒鉛の分散を良くして重なりを防正することが重要であり、そのためには黒鉛と黒鉛の間にクリンカーを配置させなければならない。 従って、黒鉛の含有量が増えるに従って、クリンカーの個数を増加させる必要があり、（１）式のように黒鉛の含有量の増加に対してクリンカーの平均粒度を制御することで、必要なクリンカーの粒子個数を確保したものである。 これによって、黒鉛間にクリンカーを配置して黒鉛の重なりを抑制し、黒鉛の酸化消失により発生する窪みを小さくすることができる。
【００１４】
本発明において、ＣａＯ−ＭｇＯ系クリンカーとしては、天然ドロマイトを出発原料とした焼結ドロマイトクリンカー、電融ドロマイトクリンカーの他に、人工原料によってＣａＯとＭｇＯの比率を任意に変更したＣａＯ−ＭｇＯクリンカーなどが使用可能である。また、ＣａＯ−ＭｇＯ系クリンカーの一部をＭｇＯ系クリンカーやＣａＯ系クリンカー、Ａｌ２Ｏ３系やＳｉＯ２系のクリンカーに置き換えることも可能である。しかしながら、Ａｌ２Ｏ３系やＳｉＯ２系のクリンカーはＣａＯと反応して低融物を生成するため、２０質量％以上の置換は好ましくない。
【００１５】
ＣａＯ−ＭｇＯ系クリンカーの一部を、各種クリンカーと置換した場合は、（１）式のクリンカーの粒度は全クリンカーの平均粒度となる。
【００１６】
黒鉛としては、鱗片状の天然黒鉛の他に、人造黒鉛、膨張黒鉛等各種黒鉛を使用することが可能である。ただし、予熱時の酸化による窪みを小さくするため、粒度は０．５ｍｍ以下である。粒度０．５ｍｍを越える黒鉛の使用は少ない方が好ましい。もし、多量に使用する場合は混合中にミキサーによって粉砕する必要がある。
【００１７】
本発明に係る連続鋳造用耐火物は、一般的な黒鉛含有の連続鋳造用耐火物の製法に準じて製造されるが、Ｃａ〇−ＭｇＯ系クリンカーの平均粒度が小さくなるにつれてクリンカーの消化（水和）が発生しやすくなるため、低湿度下で製造するか、クリンカーの表面に消化防止処理を施すことが好ましい。処理の例としては、クリンカー表面のＣａＯをＣａＣＯ３とする方法、シリコーン樹脂、ピッチ、硫酸マグネシウムなどで粒子全体を被覆する方法などがある。出発原料の混練に際しては、本発明の場合黒鉛の分散性が非常に重要なので、その点を考慮したミキサーの選定、混練条件の設定が必要である。
【００１８】
本発明の耐火物はノズル全体に適用しても良いが、アルミナ付着が問題となるのは溶鋼と接触する面であり、溶鋼と接触する面にのみ適用することも可能である。とくに、カーボン量が少ない場合は耐スポール性が低下するためノズル全体ではなく、内孔面に数ｍｍから１０数ｍｍ内張りするか、厚さ数ｍｍから１０数ｍｍのスリーブ状の耐火物を内挿する方法がより好ましい。
【００１９】
【発明の実施の形態】
本発明の実施の形態を実施例によって説明する。
【００２０】
実施例１
表１は、ＣａＯ５７質量％、ＭｇＯ４２質量％の化学成分を有するＣａＯ−ＭｇＯ系クリンカーと純度９５％の黒鉛の粒度構成の配合割合の例を示す。 同表においては、本発明の規定範囲のものを実施例１〜１１として挙げ、規定範囲外の例として比較例１〜１０として挙げている。同表に示す配合割合で秤量し、これに適量のフェノールレジンを添加してミキサーによって均一に混練して配土を得た。得られた配土をゴム型に充填し、成形圧１０００ｋｇ／ｃｍ２でＣＩＰにて成形し、最高１０００℃で還元焼成してサンプルを作製した。
【００２１】
このサンプルから、２０ｍｍ×２０ｍｍ×１７０ｍｍの試験片を切り出し、予熱時の酸化を想定して、大気中にて１２００℃で３０分熱処理を行い、試験片の表面に酸化層を形成させた。
【００２２】
高周波炉にアルミキルド鋼を１５７０℃で溶解し、溶解後アルミニウムを０．２質量％添加した溶鋼に試験片を浸漬させ１２０分後に引き上げて試験片の外観を観察し、表面へのアルミナ付着の有無を調査した結果を表１に示す。
【００２３】
【表１】
【００２４】
すなわち、黒鉛およびＣａＯ−ＭｇＯ系クリンカーを主成分とする耐火物において、耐火物中の黒鉛の含有量をａ（質量％）、ＣａＯ−ＭｇＯ系クリンカーの平均粒度をｂ（ｍｍ）としたとき、アルミナ付着を防止する連続鋳造用耐火物としては、下記（１）式を満足することが必要であることが分かる。
【００２５】
ｂ≦−０．０２×ａ＋０．８ （１）
実施例２
表１に示す実施例７と比較例７の耐火物をそれぞれ内孔に厚さ７ｍｍで配置した浸漬ノズルを作製した。これらのノズルを、最高温度１３００℃で５時間予熱したのち、鍋容量２５０ｔｏｎ、ＴＤ容量４５ｔｏｎのスラブ鋳造機による鋳造に使用した。鋳造した結果、実施例７を内張りしたノズルは１０チャージ鋳造後もアルミナの付着は皆無であった。また、鋳片の品質も良好であった。これに対して比較例７を内張りしたノズルは６チャージ目鋳造中にアルミナ付着によるノズル内孔の閉塞によりノズル交換が必要となった。回収したノズルの稼働面を調査した結果、消失した黒鉛によって生成した窪みにメタルが固着し、その上にアルミナが堆積していた。また、得られた鋳片の品質も不良であつた。
【００２６】
【発明の効果】
本発明の耐火物を使用した連続鋳造用ノズルを使用することによって、予熱時の酸化の有無に関わらず優れたアルミナ付着防止効果を発揮することができる。したがって、鋳造の安定化による鋳造コスト低減、鋳片品質の改善による品質不良率低減につながる。
【図面の簡単な説明】
【図１】 アルミナ付着の有無への黒鉛の含有量とクリンカーの平均粒度の影響を示す。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a refractory material for preventing adhesion of alumina used in a continuous casting nozzle such as a stopper used in casting molten steel, a sliding nozzle including a long stopper, an upper nozzle, a lower nozzle, an intermediate nozzle, and an immersion nozzle.
[0002]
[Prior art]
In recent years, with the stricter steel quality of aluminum deoxidized steel, so-called aluminum killed steel, which is cast as high-grade steel such as thin plates, the nozzles used to inject from tundish into molds in continuous casting Much effort has been made to prevent the adhesion of alumina.
[0003]
Alumina adhering to the nozzles coalesce, and it is taken into the molten steel flow as large inclusions, resulting in defects in the slab and reducing the quality.
[0004]
As an example of the countermeasure, there is a method of physically preventing the adhesion of alumina by blowing argon gas into the molten steel from the inner surface of the nozzle. However, in this method, if the amount of argon gas blown is too large, bubbles are taken into the slab and become pinholes in the slab. Therefore, in order to prevent the occurrence of defects in the slab, the amount of gas blowing must be limited, and this method cannot be a sufficient measure for preventing the adhesion of alumina.
[0005]
As another example of countermeasures, CaO is contained in a refractory material that constitutes a nozzle or the like used in continuous casting to have an alumina adhesion prevention function, and CaO in the refractory material reacts with alumina adhering to the nozzle. There is also known a technique for reducing adhesion of alumina by generating a low-melt material. For example, Patent Document 1 discloses a nozzle that uses a refractory material in which dolomite clinker with improved alumina adhesion prevention function and thermal shock resistance and graphite are bonded together with a carbonized matrix structure as an advanced form of this technique. Has been.
[0006]
However, this nozzle itself has an excellent alumina adhesion prevention function, but depending on the preheating conditions, the surface oxidizes and carbon disappears, and metal deposits in the dent generated there, and alumina adheres to it. As a result, the ability to prevent adhesion of alumina by the broken dolomite clinker is lost.
[0007]
The disappearance of surface carbon due to oxidation during preheating can be said to be effective by applying, as an antioxidant, a powder containing glass frit that melts to form a glass coating on the nozzle surface.
[0008]
However, when a refractory material containing a large amount of CaO is used in the nozzle, CaO in the refractory material diffuses into the melted antioxidant and lowers the viscosity of the glass coating. The anti-oxidation function may not be sufficiently exhibited due to absorption by the nozzle. Such a phenomenon is particularly likely to occur when the preheating temperature is high or the preheating time is long. In particular, the CaO—MgO-based clinker applied to the continuous casting nozzle, that is, the dromer graphite-based refractory, as described in Patent Document 1, although the graphite content is as large as 38% by weight or more, The doloma used has a relatively large particle size. For this reason, the number of doloma particles existing between graphites decreases, and the proportion of graphites overlapping each other and increasing as a large mass increases. A large lump in which graphites overlap with each other, when oxidized during preheating, a large number of large depressions are generated due to the disappearance of graphite, and the metal easily enters and adheres thereto. When the metal is fixed, the diffusion of CaO from the refractory material to the adhered alumina is hindered, so that alumina is deposited.
[0009]
[Patent Document 1]
Japanese National Patent Publication No. 11-506393 [0010]
[Problems to be solved by the invention]
An object of the present invention is to prevent a reduction in the effect of preventing alumina adhesion when graphite is oxidized and lost during preheating in a continuous casting refractory mainly composed of graphite and a CaO-MgO clinker.
[0011]
[Means for Solving the Problems]
In the present invention, in the case of a nozzle using a CaO-containing refractory, it is difficult to completely prevent oxidation at the time of preheating by the antioxidant as described above, and it is assumed that the refractory itself also loses graphite. It was completed with the recognition that taking such measures would contribute to long-term stable casting.
[0012]
That is, the present invention controls the average particle size of clinker in a refractory mainly composed of CaO-MgO clinker and graphite in accordance with the graphite content. The content of graphite in the refractory is a ( Mass%), when the average particle size of the CaO—MgO clinker is b (mm), the relationship between a and b satisfies the following formula (1).
[0013]
b ≦ −0.02 × a + 0.8 (1)
In the refractory material mainly composed of graphite and CaO-MgO-based clinker, the present invention is to improve the dispersion of graphite and prevent overlapping in order to reduce the dent generated when graphite disappears by preheating. Is important, and for that purpose a clinker must be placed between the graphites. Therefore, it is necessary to increase the number of clinker as the graphite content increases, and by controlling the average particle size of the clinker with respect to the increase in the graphite content as shown in the formula (1), The number of particles is ensured. Thereby, a clinker can be arranged between the graphites to suppress the overlap of the graphites, and the depressions generated by the oxidation disappearance of the graphites can be reduced.
[0014]
In the present invention, examples of the CaO-MgO clinker include a sintered dolomite clinker using natural dolomite as a starting material, an electrofused dolomite clinker, and a CaO-MgO clinker in which the ratio of CaO and MgO is arbitrarily changed by an artificial material. Can be used. It is also possible to replace a part of the CaO-MgO clinker with an MgO clinker, a CaO clinker, an Al 2 O 3 or SiO 2 clinker. However, Al 2 O 3 -based and SiO 2 -based clinker reacts with CaO to produce a low melt, so that substitution of 20% by mass or more is not preferable.
[0015]
When a part of the CaO-MgO clinker is replaced with various clinker, the particle size of the clinker of the formula (1) becomes the average particle size of all clinker.
[0016]
As graphite, various graphite such as artificial graphite and expanded graphite can be used in addition to scaly natural graphite. However, the particle size is 0.5 mm or less in order to reduce the depression due to oxidation during preheating. The use of graphite having a particle size exceeding 0.5 mm is preferably less. If it is used in a large amount, it must be pulverized by a mixer during mixing.
[0017]
The continuous casting refractory according to the present invention is manufactured in accordance with a general graphite-containing continuous casting refractory manufacturing method. As the average particle size of the CaO-MgO clinker decreases, the clinker digestion (water Therefore, it is preferable to manufacture under low humidity or to apply digestion prevention treatment to the surface of the clinker. Examples of the treatment include a method in which CaO on the clinker surface is CaCO3, and a method in which the entire particle is coated with silicone resin, pitch, magnesium sulfate, and the like. In kneading the starting material, the dispersibility of graphite is very important in the present invention, and therefore, it is necessary to select a mixer and set kneading conditions in consideration of this point.
[0018]
Although the refractory material of the present invention may be applied to the entire nozzle, it is possible to apply it only to the surface in contact with the molten steel, where alumina adhesion becomes a problem. In particular, when the amount of carbon is small, the spall resistance is reduced, so the inner surface of the nozzle is lined with several mm to several tens of mm, or a sleeve-like refractory with a thickness of several mm to several tens of mm is placed inside. The method of inserting is more preferable.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described by way of examples.
[0020]
Example 1
Table 1 shows an example of the blending ratio of the particle size constitution of CaO-MgO clinker having a chemical component of CaO 57 mass% and MgO 42 mass% and graphite of purity 95%. In the table, those within the specified range of the present invention are listed as Examples 1 to 11, and examples outside the specified range are listed as Comparative Examples 1 to 10. The mixture was weighed at the blending ratio shown in the table, and an appropriate amount of phenol resin was added thereto, and the mixture was uniformly kneaded with a mixer to obtain a soil distribution. The obtained soil distribution was filled in a rubber mold, molded with CIP at a molding pressure of 1000 kg / cm 2 , and reduced and fired at a maximum of 1000 ° C. to prepare a sample.
[0021]
From this sample, a test piece of 20 mm × 20 mm × 170 mm was cut out and subjected to heat treatment at 1200 ° C. for 30 minutes in the atmosphere assuming oxidation during preheating to form an oxide layer on the surface of the test piece.
[0022]
The aluminum killed steel is melted at 1570 ° C. in a high-frequency furnace, and after melting, the test piece is immersed in molten steel to which 0.2% by mass of aluminum is added, pulled up after 120 minutes, and the appearance of the test piece is observed. The results of the investigation are shown in Table 1.
[0023]
[Table 1]
[0024]
That is, in a refractory mainly composed of graphite and CaO—MgO clinker, when the content of graphite in the refractory is a (mass%) and the average particle size of the CaO—MgO clinker is b (mm), It can be seen that the continuous casting refractory for preventing alumina adhesion needs to satisfy the following formula (1).
[0025]
b ≦ −0.02 × a + 0.8 (1)
Example 2
An immersion nozzle was prepared in which the refractories of Example 7 and Comparative Example 7 shown in Table 1 were respectively disposed in the inner holes with a thickness of 7 mm. These nozzles were preheated at a maximum temperature of 1300 ° C. for 5 hours, and then used for casting by a slab casting machine having a pan capacity of 250 tons and a TD capacity of 45 tons. As a result of casting, the nozzle lined with Example 7 showed no alumina adhesion even after 10 charge casting. The quality of the slab was also good. On the other hand, the nozzle lined with Comparative Example 7 needed to be replaced due to the blockage of the nozzle bore due to the adhesion of alumina during casting of the sixth charge. As a result of investigating the operating surface of the recovered nozzle, metal was fixed to the depression generated by the disappeared graphite, and alumina was deposited thereon. Moreover, the quality of the obtained slab was also inferior.
[0026]
【Effect of the invention】
By using the continuous casting nozzle using the refractory of the present invention, an excellent alumina adhesion preventing effect can be exhibited regardless of the presence or absence of oxidation during preheating. Therefore, the casting cost is reduced by stabilizing the casting, and the quality defect rate is reduced by improving the slab quality.
[Brief description of the drawings]
FIG. 1 shows the influence of graphite content and clinker average particle size on the presence or absence of alumina adhesion.
Claims (1)
耐火物中の粒度が０．５ｍｍ以下の黒鉛の含有量をａ（質量％）、ＣａＯ−ＭｇＯ系クリンカーの平均粒度をｂ（ｍｍ）とした場合、下記（１）式を満すように、前記クリンカーの平均粒度を黒鉛の含有量に合わせて制御した連続鋳造用ノズルに用いられるアルミナ付着を防止する耐火物。
ｂ≦−０．０２×ａ＋０．８ （１）In a refractory material for preventing adhesion of alumina used in a continuous casting nozzle composed of graphite in which graphite and CaO-MgO clinker are combined with a carbonized matrix structure and CaO-MgO clinker having chemical components of CaO and MgO ,
When the content of graphite having a particle size of 0.5 mm or less in the refractory is a (mass%) and the average particle size of the CaO-MgO clinker is b (mm), the following equation (1) is satisfied. A refractory for preventing alumina adhesion used in a continuous casting nozzle in which the average particle size of the clinker is controlled in accordance with the graphite content.
b ≦ −0.02 × a + 0.8 (1)
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| JP4519109B2 (en) * | 2006-06-26 | 2010-08-04 | 日新製鋼株式会社 | Stopper control type immersion nozzle |
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| JP3265239B2 (en) * | 1997-09-05 | 2002-03-11 | 品川白煉瓦株式会社 | Immersion nozzle for continuous casting |
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